People should know what this actually does.
When your computer (or iPod or iPad) contacts any server, like the App Store, it first needs to know where the App Store is. To find out, it asks a special server, the "DNS server". Usually it is the DNS server run by your ISP. Sometimes that DNS server doesn't work properly. If the DNS store doesn't tell where the App Store is, you can't use the App Store, and nothing Apple can do about it. The App Store works just fine, just your computer cannot find it.
8.8.8.8 is the address of a DNS server run by Google. I have no idea if it is any better or worse than your ISP's DNS server, but if every server works 99% of the time, and your ISP's DNS server doesn't work right now, then switching to _any_ other DNS server is most likely to fix the problem. If one day 8.8.8.8 doesn't work, then switching back to your ISP will also most likely fix the problem.
Legal responsibility. It's quite obvious that Apple isn't worried about jailbreaking too much, otherwise these fixes would have happened a lot earlier. A while ago there was a jailbreak through a website, which indicates a truly dangerous exploit, and that was fixed _very_ quickly, so Apple _can_ do this quickly if they want to. But right now, if anything goes wrong with your jailbreak, Apple can say "not our problem". If a jailbreak was official, any problem you have would be Apple's problem.